The 13th Annual San Antonio Breast Cancer Symposium is an international meeting featuring state-of-the art lectures by invited speakers and proffered papers on the experimental biology, etiology, prevention, diagnosis and therapy of breast cancer. The symposium features concurrent clinical and basic science sessions as well as clinically oriented panel discussions during lunch. Abstracts accepted for presentation and manuscripts of plenary lectures are published in the journal BREAST CANCER RESEARCH AND TREATMENT. All symposia to date have been granted Category 1, AMA credit for continuing education. The 1989 symposium enrolled 628 registrants representing the United States and Canada, and twenty foreign countries.